JPH0219575B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a shadow mask for mask-focused color image reception, and more specifically, the present invention relates to a method for forming a shadow mask for mask-focused color image reception. The present invention relates to a method for forming a shadow mask for a mask focusing type color picture tube, in which an electron lens is formed in an electron beam passage hole of a mask focusing type color picture tube.

The shadow mask of the mask-focusing color picture tube has two electrodes, a shadow mask electrode and a shadow mask lens electrode, facing each other, and a predetermined potential difference is applied between them to form an electron lens in the electron beam passage hole. Such shadow masks are disclosed in Japanese Patent Publication No. 45-4819, Japanese Patent Publication No. 20451-1982, Publication No. 8261-1982, Publication No. 28188-1988, Publication No. 28789-1989, etc. There is. To explain these based on FIG. 1, a shadow mask electrode 1 and a shadow mask lens electrode 2 are opposed to each other with an insulator 3 in between. A large number of passage holes 8 are provided. Opposed to this shadow mask, a three primary color phosphor layer 5 and a metal back layer 6 are provided on the face glass 4 of the picture tube.

In the picture tube having the above structure, an accelerating voltage or a voltage close to it is applied to the shadow mask lens electrode 2, and a voltage lower than that of the shadow mask lens electrode 2 is applied to the shadow mask electrode 1, so that the electron beam passage hole is 8, electric lines of force shown by arrows are generated and an electrostatic lens is formed. The electron beam traveling through each hole where such an electric field exists is focused toward the central axis of the hole by the action of the electrostatic lens and collides with the phosphor layer 5. The diameter of the electron beam at the time of this collision becomes considerably smaller than the area of the passage hole 8 due to the above-mentioned focusing effect. By using a shadow mask having the above structure, it is possible to increase the utilization rate of electron beams, obtain a bright screen, and further improve color purity and resolution. In a mask focusing type color picture tube, when two electrodes are made to face each other, if the targeted electron beam passage holes are not perfectly matched, the electrostatic lens effect will be weakened and the shape of the focused electron beam will be distorted, resulting in poor image quality. Not only is this not desirable, but it also has the potential to cause a landing error of the electron beam on the fluorescent surface.

In general, shadow masks for mask-focusing color picture tubes are molded to have a certain curvature just like normal color picture tubes, but as an example of this method, U.S. Pat. No. 4,112,563 describes a method in which each mask is stretched independently A method is shown in which a mold having a certain curvature is pushed up from below through a sheet with a metal layer formed on both sides of the insulating layer and a metal layer serving as a heat diffusion bonding agent is formed between two masks, and the mold is passed through a high-temperature furnace while being pressed. has been done. However, pulling both ends of the mask flat with a constant tension means that the stress applied to the entire mask differs, and pushing up and crimping the mating mold will apply even greater strain stress, which may cause variations in the elongation of the mask holes. Occur.
As a result, distortion occurs in the electron beam passage hole, resulting in a drawback that no improvement in image quality can be expected.

As mentioned above, in the case of a structure in which an insulating material such as glass or polyimide film is interposed between two shadow masks, when an electron beam collides with this insulating material, the insulating material becomes electrically charged and a sufficient electron beam focusing effect is obtained. This has the drawback that not only does it not work, but it also causes astigmatism, making it impossible to take advantage of the extremely excellent advantages provided by this structure. On the other hand, two shadow masks are laid flat without an insulator interposed between them, the electron beam passage holes are aligned, and then molded using a press in the same way as a normal color picture tube shadow mask. In the case of a structure that allows a desired spacing between the shadow masks, the disadvantage is that the electron beam passage hole is distorted due to variations in slippage and elongation between the two masks during pressing, making it impossible to expect improvement in image quality. have

The present invention relates to a method of forming a shadow mask for a mask focusing type color picture tube in which a constant distance is maintained between two shadow mask electrodes facing each other without an insulator interposed therebetween.

That is, the present invention has been made in view of the above points, and the purpose is to avoid distortion during press molding to have a desired curvature after overlapping two shadow mask electrodes and aligning the electron beam passage hole. The present invention provides a method for forming a shadow mask for a mask-focusing color picture tube, which provides an electron beam passage hole that allows the electron beam to pass through.

The details of the present invention will be described below with reference to Examples. Note that the other configurations of the color picture tube are the same as those shown in FIG. 1, so explanations will be omitted.

A shadow mask electrode having a desired hole is formed by photo-etching in the same way as a normal color picture tube shadow mask, and the shadow mask is located outside the mask effective surface 11 in order to easily align the electron beam passage hole. A matching guide hole 14 is provided. Next, as shown in FIG. 2, after overlapping the two masks 1 and 2 using a positioning jig 9 equipped with a guide pin 10, electrons due to misalignment between the masks during pressing to create a desired curvature are generated. Seam welding 1 around the area other than the mask effective surface 11 to prevent distortion of the beam passage hole
2 or spot weld 13 to fix the two masks together. An example of welding positions is shown in Figure 3. After this, press molding is performed using male and female molds with the desired curvature, as in the case of normal color picture tube shadow mask molding. Cut using. When comparing the two masks formed using this method, the curvature of the mask for color picture tubes is different due to the difference in the curvature of the plate thickness, so microscopically there are non-uniformities in the shadow mask material and differences in the way pressure is applied during pressing. Due to this, there will be some variation in the elongation of the mask hole. However, when the electron beam passage hole is large, the reduction in the electrostatic lens effect caused by the distortion of the electron beam passage hole due to this variation in elongation was within a negligible range.
However, when the electron beam passage hole is small, the distortion of the electron beam passage hole caused by the above method cannot be ignored and becomes a serious problem.

A more accurate shadow mask forming method that does not compensate for the drawbacks of the above-mentioned methods will be described below.

A shadow mask electrode with a desired hole is formed by photo-etching in the same way as a normal color picture tube shadow mask, and in order to easily align the electron beam passage hole, this shadow mask has a hole located outside the effective surface of the mask. A matching guide hole is provided. Next, as shown in Figure 2, the mask is effective to prevent distortion of the electron beam passage hole due to misalignment of the two masks during pressing to give the desired curvature after overlapping the two masks using an alignment jig. The two masks are fixed together by seam welding or spot welding around the outside of the plane. The steps up to this point are the same as the molding method described above.

Next, as shown in FIG.
Fill with resin 15. Examples of resins used for this include phenol, epoxy, polyvinyl, vinyl acetate, cellulose, and polyamide resins. However, the resin used must be easily removed after press molding, and as a result of various experiments, it was found that polyvinyl alcohol resin was suitable. By filling the electron beam passage hole with polyvinyl alcohol resin and thoroughly drying it with hot air at approximately 100°C, sufficient effects were achieved in terms of adhesive strength to the electron beam passage hole wall and fracture resistance during pressing. However, it is desirable to cure this resin in order to prevent minute misalignment during pressing of the two masks. This curing method involves using formalin solution after drying with hot air.
Immersion or spraying in tannic or chromic acid solutions is preferred. Thereafter, pressing is carried out using male and female molds having the desired curvature to obtain the desired curvature, in the same manner as in the molding of ordinary color picture tube shadow masks. After this, the filled resin is removed and the outside of the effective surface, including the welded part, is cut mechanically or using a laser beam. However, when polyvinyl alcohol resin is used, the molded shadow mask is removed using an alkaline solution such as hydroxide. Preferred methods include immersion or spraying in sodium, potassium hydroxide, aqueous ammonia or aqueous hydrogen peroxide. In the mask-focusing type color picture tube shadow mask formed by this method, even slight deviations in the elongation of the mask holes during pressing occur in a one-to-one manner between the two masks, so in the end, the desired electron beam passing hole cannot be formed. I was able to get it.

As described above, according to the present invention, in the shadow mask forming method for a mask focusing type color picture tube, which improves the electron beam utilization rate by forming an electron lens in the electron beam passage hole and narrowing down the electron beam, two sheets are used. When molding a mask focusing type color picture tube shadow mask with a structure that does not require an insulator between the shadow mask electrodes, distortion of the electron beam passage hole due to misalignment and uneven elongation of the two shadow masks during press molding can be prevented. The electron beam passing hole is obtained, the effect of the mask focusing type color picture tube shadow mask can be fully exhibited, and a good image can be reproduced, which is very effective.

[Brief explanation of drawings]

Fig. 1 is a partially enlarged view showing the shadow mask or face glass of a mask focusing color picture tube, Fig. 2 is a schematic view showing a shadow mask electrode positioning jig according to an embodiment of the present invention, and Fig. 3 is a welding position as well. FIG. 4 is a schematic view showing an example, and FIG. 4 is a partial cross-sectional view similarly showing the shadow mask forming process. DESCRIPTION OF SYMBOLS 1...Shadow mask electrode, 2...Shadow mask lens electrode, 3...Insulator, 4...Face glass, 5...Tricolor phosphor layer, 6...Metal back layer, 7...Electron beam, 8 ...Electron beam passage hole, 9...Positioning jig, 10...Guide pin,
11... Mask effective surface, 12... Seam welding, 1
3...Spot welding, 14...Positioning guide hole.

Claims (1)

[Claims] 1. In a shadow mask forming method for a mask focusing type color picture tube, in which an electrostatic lens is formed by fixing two shadow mask electrodes at a constant interval and creating a potential difference between the electrodes. , the above-mentioned two shadow mask electrodes are overlapped, the outside of the effective surface of the mask is seam welded or spot welded, and then formed to have a desired curvature, and the outside of the effective surface of the mask, including the welded portion, is cut after forming. A shadow mask molding method for mask focusing color picture tubes. 2 Overlap two shadow mask electrodes, seam weld or spot weld the outside of the effective surface of the mask, fill the electron beam passage hole with resin, shape it to have a desired curvature, and then remove the resin inside the electron beam passage hole. 2. The method of forming a shadow mask for a mask focusing type color picture tube according to claim 1, wherein the mask is then cut outside the effective mask surface including the welded portion.